Stellar populations of the globular cluster NGC 5053 investigated using AstroSat-Ultra Violet Imaging Telescope. (arXiv:2205.13839v2 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Nikitha_K/0/1/0/all/0/1">K. J. Nikitha</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Vig_S/0/1/0/all/0/1">S. Vig</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Ghosh_S/0/1/0/all/0/1">S. K. Ghosh</a> (2) ((1) Indian Institute of Space science & Technology (IIST), Thiruvananthapuram, India, (2) Tata Institute of Fundamental Research (TIFR), Mumbai, India)
Globular clusters being old and densely packed serve as ideal laboratories to
test stellar evolution theories. Although there is enormous literature on
globular clusters in optical bands, studies in the ultraviolet (UV) regime are
sparse. In this work, we study the stellar populations of a metal poor and a
rather dispersed globular cluster, NGC 5053, using the UV instrument of
AstroSat, namely the Ultra Violet Imaging Telescope in three far-UV (F154W,
F169M, F172M) and three near-UV (N219M, N245M, N263M) filters. Photometry was
carried out on these images to construct a catalogue of UV stars, of which the
cluster members were identified using Gaia EDR3 catalogue. UV and optical CMDs
help us locate known stellar populations such as BHB stars, RR-Lyrae stars, RHB
stars, BSSs, SX-Phe, RGB and AGB stars. Based on their locations in the CMDs,
we have identified 8 new BSS candidates, 6 probable eBSSs, and an EHB
candidate. Their nature has been confirmed by fitting their spectral energy
distributions with stellar atmospheric models. We believe the BSS population of
this cluster is likely to have a collisional origin based on our analyses of
their radial distribution and SEDs. BaSTI-IAC isochrones were generated to
characterize the cluster properties, and we find that the observed brightness
and colours of cluster members are best-fit with a model that is alpha-enhanced
with a helium fraction of 0.247, metallicity of -1.9 dex and age within a range
of 10.5-14.5 Gyr.
Globular clusters being old and densely packed serve as ideal laboratories to
test stellar evolution theories. Although there is enormous literature on
globular clusters in optical bands, studies in the ultraviolet (UV) regime are
sparse. In this work, we study the stellar populations of a metal poor and a
rather dispersed globular cluster, NGC 5053, using the UV instrument of
AstroSat, namely the Ultra Violet Imaging Telescope in three far-UV (F154W,
F169M, F172M) and three near-UV (N219M, N245M, N263M) filters. Photometry was
carried out on these images to construct a catalogue of UV stars, of which the
cluster members were identified using Gaia EDR3 catalogue. UV and optical CMDs
help us locate known stellar populations such as BHB stars, RR-Lyrae stars, RHB
stars, BSSs, SX-Phe, RGB and AGB stars. Based on their locations in the CMDs,
we have identified 8 new BSS candidates, 6 probable eBSSs, and an EHB
candidate. Their nature has been confirmed by fitting their spectral energy
distributions with stellar atmospheric models. We believe the BSS population of
this cluster is likely to have a collisional origin based on our analyses of
their radial distribution and SEDs. BaSTI-IAC isochrones were generated to
characterize the cluster properties, and we find that the observed brightness
and colours of cluster members are best-fit with a model that is alpha-enhanced
with a helium fraction of 0.247, metallicity of -1.9 dex and age within a range
of 10.5-14.5 Gyr.
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